This research project will focus on the role or phosphorylation on regulation of key cell proliferation factors such as Myc, c-Jun, and cyclin D. It has been demonstrated that the ubiquitin/proteasome pathway degrades Myc. For this targeting to occur, sequential phosphorylation is required. Furthermore, we suggest a role of both an isomerase such as Pin 1 and a phosphatase such as PPA2 in this regulation. These factors will be identified. In addition, the ubiquitin ligase complex required for ubiquitination of Myc will be identified. Finally, I will determine if this pathway is a common mechanism utilized in the control of other determined of this pathway is a common mechanism utilized in the control of other key cell proliferation factors.